Brian, details of fault appreciated.
Re the right turn - as discussed in detail in previous posts, plotting on charts gives waypoint change posn to crash site as about 035 mag - which was on the handling pilots HSI course selector - anyone in general aviation should recognise this as evidence that pilot was intentionally going on that course.
That it was on this setting by coincidence is hard to believe, especially as up to waypoint change 027 would have been the likely setting as that track was spot on for getting from Aldergrove to that position - this is basic nav with such instruments.
I believe that the course setting is a significant clue.
It also suggests that there was something in that direction to work off - there was no stored waypoint in the SuperTANS to account for it and no known fixed radio aid - hence suspicion of kit I have suggested.
Add to this the factors that it was slowing down (airspeed wise, Boeing analysis), there being a known LZ used by Chinooks at waypoint A, one RADALT alarm on min as per immediate landing, handling pilots baro alt set to give zero at alt of that LZ.
Something extra was going on.